“Congress needs more strong women like Katherine Clark to help fight the Tea Party," Schwartz said in a release. "I know Katherine will be a strong voice for pay equity, protecting Medicare, college affordability and other issues that affect families every single day.”

Schwartz's backing marks the latest progressive woman to endorse Clark's candidacy. Clark has already received the support of Massachusetts Attorney General Martha Coakley and EMILY's List, a group that boosts female Democratic candidates who support abortion rights.

Clark and four other Democrats — state Sens. Karen Spilka and William Brownsberger, Middlesex County Sheriff Peter Koutoujian and state Rep. Carl Sciortino – are running in the Oct. 15 Democratic primary to replace Edward J. Markey, who was elected to the Senate in June.

The Democratic primary will likely select the next member of Congress from this deep blue district in the Boston suburbs.

Massachusetts' 5th District is rated a Safe Democratic contest by Rothenberg Political Report/Roll Call.